Key Engineering Materials Vols. 392-394

Abstract: A variable interval fuzzy quantification algorithm with self-adjustable factor in full domain is proposed in this paper. It focuses on digital inverted plasma arc cutting power and studies strong nonlinearity and uncertainty of power. The neural network is also introduced to decouple cutting parameters variables in the multi-parameters coupling cutting process. This algorithm avoids complex nonlinear system modeling and realizes real-time and effective online control of cutting process by combining advantages of fuzzy control and neural network control. Furthermore, the optimized fuzzy control improves steady-state precision and dynamic performance of system simultaneously. The experimental result shows that this control improves precision, ripples, finish and other comprehensive index of work piece cut, and plasma arc cutting power supply based on fuzzy-neural network has excellent control performance.

Abstract: B-spline method plays an important role in data interpolating, fitting and smoothing. Through analyzing the computed path of the de Boor-Cox algorithm, a new method for calculating B-spline function is given based on the vector extending operation. The proposed method has a parallel computing architecture and is suitable to realize by computers. Compared with the de Boor-Cox algorithm, the proposed method can improve computing efficiency by (2k+1) times in the task of calculating all nonzero values of k-degree B-spine functions. As an application in B-spline curve fitting, it shows that the proposed algorithm can reduce the computing efforts obviously.

Abstract: Aiming at hole filling in points cloud data reconstruction, a novel neural network arithmetic was employed in abridged points cloud data surface reconstruction. Radial basis function neural network and simulated annealing arithmetic was combined. Global optimization feature of simulated annealing was employed to adjust the network weights, the arithmetic can keep the network from getting into local minimum. MATLAB program was compiled, experiments on abridged points cloud data have been done employing this arithmetic, the result shows that this arithmetic can efficiently approach the surface with 10-4 mm error precision, and also the learning speed is quick and hole filling algorithm is successful and the reconstruction surface is smooth. Different methods have been employed to do surface reconstruction in comparison, the results illustrate the error employed algorithmic proposed in the paper is little and converge speed is quick.

Abstract: A scheduling approach using genetic algorithms (GA) was presented to optimize multiple projects for quality project period performance with resource constraints. The model of the approach and key parameters of the algorithm including chromosome encoding and decoding, fitness computation, initial population, selection and crossover were conducted. A precedence feasible list was used in the chromosome encoding and decoding operation to reduce search space. An efficient crossover method was developed to avoid the procedure of chromosome recovery. A comparison was made between the algorithm and a heuristic scheduling method with an example. The result validates the superiority of the approach.

Abstract: There is a magnetic field inside thrust bearing. The magnetic field distribution is one of the key factors which decide the running state and performance. With the finite element of ANSYS software, the magnetic field of thrust bearing has been analyzed. The rule of changes between the magnetic field and the influencing factors has been discovered. The analysis shows that the direction of exciting current should be opposite other than identical. The greater the ratio of gap length between stator and rotor and working gap length is, the less magnetic field leakage is. The flux leakage of thrust bearing attains 37 percent when the ratio of the gap is 4.0. If the design of a complete machine is not proper, the flux leakage may attain 20 percent upwards through other gaps although that of the bearing itself is almost zero. Calculation of bearing capacity indicates that theoretical value is not exact due to its neglect of magnetic saturation and flux leakage, while FEM value comparably matches the real substance with considering the magnetic saturation and flux leakage. The research provides the theoretical basis for optimization of system structure and selection of current direction control.

Abstract: Electric steering engine was generally applied in arm systems such as carrier rocket and missile, its life period is very short, and the space and weight of its reducer were strictly restricted, so it is not fit to adopt the conventional rule of infinite life to design electric steering engine gear reducer. This paper carried out the optimum design for it based on the rule of finite life and space, provided and demonstrated a new design scheme, and realized the interior overall structure design of reducer. We used the UG plane to realize three-dimension module design and virtual assembly of gear reducer, elaborated the implementation method of three-dimension motion simulation by the parameter drive mechanism, and simulated the actual working procedure. Experimental results indicated that this gear reducer satisfied excellently the requirement of big drive ratio under the finite life and space.

Abstract: Expected path of polishing tool is one of the most essential needs for movement scheduling and movement controlling of polishing robot in free-form surfaces polishing. By analyzing the expected movement and position of polishing tool and based on the traditional movement scheduling methods, this paper carries out systematic research works on contour-parallel-machining tool path planning method and direction-parallel-machining tool path planning method for polishing tool paths figuring out. Compared with contour-parallel-machining tool path planning method, the direction-parallel-machining tool path planning method needs one less number of degree of freedom and is much easier to avoid physical interventions and mechanic singularity, so it is an improved one.

Abstract: This paper studies the problem of motion planning of wheeled mobile robot (WMR), which is driven by double wheels separately. It mainly accomplish the motion planning of WMR by taking center of one of double wheels as a base point, and also carry out this problem by traditional method, which takes the midpoint of interval between two wheels as a base point. Besides, these two motion planning methods are compared. Experimental results show that the first motion planning method is simply controlled, saves much computer time and it establishes the foundation to solve the problem of real time control to WMR.

Abstract: The crux of injection mold production is scheduling, which should be made before the mold manufacturing. Generally, a mold part has some operations subject to certain sequence constraints. Furthermore, some operations have to satisfy process combination constraints with one or more other operations. The expression method of operation constraints is studied. If genetic algorithm is employed to solve scheduling problems in injection mold manufacturing, invalid chromosome representation during the computing period of population initialization and the crossover, mutation will generated unavoidably. An adjustment algorithm is proposed to ensure the validity of chromosome representation. Any chromosome representation based on operation or workpiece could be adjusted to a valid operation sequence by this algorithm. The feasibility of the algorithm is validated by computing cases.

Abstract: The architecture and operation theory of Giant Magnetostrictive Accurate-motion Actuator have been introduced. After analysing the driving characteristic of giant magnetostrictive material and requirement of driving power, a design method of wide range and high precision NC constant-current source has been put out. The output circuit is composed of serial 12-bit DACs Max531, low-noise high-speed precision operational amplifiers OP27 and driving circuit. It provides current from 0 to 2.048A with 0.5mA step value. Two fully differential input channels 16-bit, sigma-delta ADCs AD7705 collects output current in feedback loop. Current ripple is controlled under 0.25mA through using homemade high-performance linear power. The result shows that the driving power with characteristic of high stability and fast response meets the needs of driving of Giant Magnetostrictive Accurate-motion.